Spatio-temporal hotspots of satellite-tracked arctic foxes reveal a large detection range in a mammalian predator.

Lai S, Bêty J, Berteaux D - Mov Ecol (2015)

Bottom Line:
The scale at which animals perceive their environment is a strong fitness determinant, yet few empirical estimates of animal detection ranges exist, especially in mammalian predators.Using daily Argos satellite tracking of 26 adult arctic foxes (Vulpes lagopus) during a single winter in the High Canadian Arctic, we investigated the detection range of arctic foxes by detecting hotspots of fox activity on the sea ice.Foxes often traveled more than 10 km, and up to 40 km, to reach hotspots, which lasted one-two weeks and could gather up to 12 individuals.

Background: The scale at which animals perceive their environment is a strong fitness determinant, yet few empirical estimates of animal detection ranges exist, especially in mammalian predators. Using daily Argos satellite tracking of 26 adult arctic foxes (Vulpes lagopus) during a single winter in the High Canadian Arctic, we investigated the detection range of arctic foxes by detecting hotspots of fox activity on the sea ice.

Results: While maintaining territories in the tundra, these solitary foragers occasionally used the sea ice where they sometimes formed spatio-temporal hotspots, likely scavenging on marine mammal carcasses. We detected 35 movements by 13 individuals forming five hotspots. Foxes often traveled more than 10 km, and up to 40 km, to reach hotspots, which lasted one-two weeks and could gather up to 12 individuals. The likelihood of a fox joining a hotspot was neither influenced by its distance from the hotspot nor by the distance of its home range to the coast.

Conclusions: Observed traveling distances may indicate a high detection range in arctic foxes, and our results suggest their ability to detect food sources on the sea ice from their terrestrial home range. While revealing a wide knowledge gap regarding resource detection abilities in mammalian predators, our study provides estimates of detection range useful for interpreting and modeling animal movements. It also allows a better understanding of foraging behavior and navigation capacity in terrestrial predators.

Fig3: Frequency distribution of distances traveled by foxes to reach spatio–temporal hotspots on the sea ice. The 35 movements shown were performed by 13 arctic foxes moving to five spatio–temporal hotspots on the sea ice of Navy Board Inlet (Nunavut, Canada) during winter 2010–2011

Mentions:
Thirty–five movements to the sea ice by 13 individuals formed five spatio–temporal hotspots on the land–fast ice of Navy Board Inlet (Fig. 2). Four to 12 foxes visited a given hotspot, with a maximum of nine foxes present on the same day at Hotspot–1 (Fig. 2a). Foxes traveled on average 11.9 ± 9.9 km (range: 1.6–40.6 km, n = 35; Fig. 3) to join a hotspot. The maximum, 40.6 km travel distance, was recorded for a fox joining Hotspot–3 in January. The hotspots lasted 12 ± 3.3 days (range: 8–17 days) and individual foxes were present on average 2.8 ± 1.8 days at a given hotspot. The date of arrival and the minimum number of days spent at a site (1 to 8 days), however, varied considerably among individuals (Fig. 2). In 16 (45.7 %) of 35 instances when a fox joined a hotspot, the individual visited two or three times, with trips back to the territory between visits. Neither the distance of a fox to a hotspot, nor the distance between a fox territory and the coast influenced the likelihood of that fox joining the hotspot (respectively, coefficient −0.07, SE 0.05; χ2 = 1.48, df = 1, p = 0.22 and coefficient −0.43, SE 0.29; χ2 = 3.03, df = 1, p = 0.08). Foxes arriving late at a hotspot stayed fewer days than those arriving early. On average, a fox decreased the length of its stay at a hotspot by 1 day for every 4 days passing since the beginning of the hotspot (coefficient −0.23, SE 0.08; χ2 = 4.16, df = 1, p = 0.04). However, the distance a fox traveled to a hotspot did not influence the length of its stay (coefficient 0.01, SE 0.01; χ2 = 0.94, df = 1, p = 0.33).Fig. 3

Fig3: Frequency distribution of distances traveled by foxes to reach spatio–temporal hotspots on the sea ice. The 35 movements shown were performed by 13 arctic foxes moving to five spatio–temporal hotspots on the sea ice of Navy Board Inlet (Nunavut, Canada) during winter 2010–2011

Mentions:
Thirty–five movements to the sea ice by 13 individuals formed five spatio–temporal hotspots on the land–fast ice of Navy Board Inlet (Fig. 2). Four to 12 foxes visited a given hotspot, with a maximum of nine foxes present on the same day at Hotspot–1 (Fig. 2a). Foxes traveled on average 11.9 ± 9.9 km (range: 1.6–40.6 km, n = 35; Fig. 3) to join a hotspot. The maximum, 40.6 km travel distance, was recorded for a fox joining Hotspot–3 in January. The hotspots lasted 12 ± 3.3 days (range: 8–17 days) and individual foxes were present on average 2.8 ± 1.8 days at a given hotspot. The date of arrival and the minimum number of days spent at a site (1 to 8 days), however, varied considerably among individuals (Fig. 2). In 16 (45.7 %) of 35 instances when a fox joined a hotspot, the individual visited two or three times, with trips back to the territory between visits. Neither the distance of a fox to a hotspot, nor the distance between a fox territory and the coast influenced the likelihood of that fox joining the hotspot (respectively, coefficient −0.07, SE 0.05; χ2 = 1.48, df = 1, p = 0.22 and coefficient −0.43, SE 0.29; χ2 = 3.03, df = 1, p = 0.08). Foxes arriving late at a hotspot stayed fewer days than those arriving early. On average, a fox decreased the length of its stay at a hotspot by 1 day for every 4 days passing since the beginning of the hotspot (coefficient −0.23, SE 0.08; χ2 = 4.16, df = 1, p = 0.04). However, the distance a fox traveled to a hotspot did not influence the length of its stay (coefficient 0.01, SE 0.01; χ2 = 0.94, df = 1, p = 0.33).Fig. 3

Bottom Line:
The scale at which animals perceive their environment is a strong fitness determinant, yet few empirical estimates of animal detection ranges exist, especially in mammalian predators.Using daily Argos satellite tracking of 26 adult arctic foxes (Vulpes lagopus) during a single winter in the High Canadian Arctic, we investigated the detection range of arctic foxes by detecting hotspots of fox activity on the sea ice.Foxes often traveled more than 10 km, and up to 40 km, to reach hotspots, which lasted one-two weeks and could gather up to 12 individuals.

Background: The scale at which animals perceive their environment is a strong fitness determinant, yet few empirical estimates of animal detection ranges exist, especially in mammalian predators. Using daily Argos satellite tracking of 26 adult arctic foxes (Vulpes lagopus) during a single winter in the High Canadian Arctic, we investigated the detection range of arctic foxes by detecting hotspots of fox activity on the sea ice.

Results: While maintaining territories in the tundra, these solitary foragers occasionally used the sea ice where they sometimes formed spatio-temporal hotspots, likely scavenging on marine mammal carcasses. We detected 35 movements by 13 individuals forming five hotspots. Foxes often traveled more than 10 km, and up to 40 km, to reach hotspots, which lasted one-two weeks and could gather up to 12 individuals. The likelihood of a fox joining a hotspot was neither influenced by its distance from the hotspot nor by the distance of its home range to the coast.

Conclusions: Observed traveling distances may indicate a high detection range in arctic foxes, and our results suggest their ability to detect food sources on the sea ice from their terrestrial home range. While revealing a wide knowledge gap regarding resource detection abilities in mammalian predators, our study provides estimates of detection range useful for interpreting and modeling animal movements. It also allows a better understanding of foraging behavior and navigation capacity in terrestrial predators.